Various types of door locks are commercially available, of which the most commonly used two types are a spring-loaded, latch bolt type and a toggle-operated dead bolt type. The locks of latch bolt type mainly comprise a spring-loaded lock bolt having a tapered head, and are commonly used for latching the door on closing. The locks of dead bolt type are operable only with a key or an operating handle provided therewith. The locks of latch bolt type provide the convenience of latching the door automatically on closing, but they provide less security as their tapered, spring loaded latch can be pushed back with a thin tool. The locks of dead bolt type provide better security as their bolt can not be retracted without a key or the operating handle readily provided with the locks, but they lack the convenience of latching or locking the door on closing. Therefore, it has become a common and costly practice to install both types of locks on a door in most houses and buildings.
In view of the above mentioned shortcomings of conventional door locks, the present invention proposes a novel door lock construction which eliminates these shortcomings.